Item frames not dropping/glitching when dropping

I was placing some item frames above my brewing stands in my house in my survival world, and when I placed one where I didn't mean to, I broke it to place it where I wanted it.

What I expected to happen was...:
When hit, the item frame would break off the wall and drop on the floor.

What actually happened was...:
Several things, from different times I took the item frame off the wall. Once, it flew from side to side, above and between two brewing stands, in a glitchy manner, and after a few seconds dropped some three to four blocks away. Another time, I had placed it in the same block as a sign, and it didn't drop at all.

Steps to reproduce:
1. Make a wall of any solid block. I was using Stone Bricks. Place some brewing stands on the floor by the wall.
2. Place an item frame on the wall.
3. Punch it to break it, and notice how it seems to glitch above the brewing stands as it drops.
4. Place a sign on the wall, and then place the item frame on the same block. Punch the item frame, and notice how it does not drop anything.

Notes: Though I'm not sure, the glitchy dropping may have been caused by the nature of the brewing stands (not a solid block). The lack of drop may have been caused by the sign, which was in the same block.